Method of making abrasive teeth



Nov. 15, 1949 WEBSTER 2,488,151

METHOD OF MAKING ABRASIVE TEETH Filed Dec. 4, 1945 zshe xs-sheet 1 H9- 3 DUANE 6 WEBSTERQMW Nov. 15, 1949 D. E. WEBSTER 2,488,151

METHOD OF MAKING ABRASIVE TEETH Filed Dec. 4, 19,45 2' sheetssms 2 W ZV M 00AM Z WEBSTZRJMW.

Patented Nov. 15,1949

UNITED STATES PATENT OFFICE METHOD OF MAKING ABRASIVE TEETH Duane E. Webster, Worcester, Mass., assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Application December 4, 1945, Serial No. 632,711

1 Claim. 1

The invention relates to metallurgical processes particularly for the manufacture of diamond abrasive inserts, cutting teeth, wheels and the like.

One object of the invention is to provide a method for strongly attaching a diamond impregnated piece to a holding member. Another object of the invention is to provide a method particularly useful for the manufacture of a composite abrasive article, i. e., where the complete article, be it a wheel, a band saw or any other species, consists of a quantity of diamond abrasive units.

Another object of the invention is to make articles of the class indicated cheaply and expeditiously. Another object of the invention is to make a diamond abrasive inserted tooth or the like in which the abrasive piece is secured to the backing member with a stronger union than has hitherto been found possible. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claim.

In the accompanying drawings illustrating the manufacture of a particular article by means of the Process of this invention,

Figure 1 is an end elevation of the separate parts from which an abrasive tooth may be made in accordance with this invention;

Figure 2 is a plan view showing the parts of Figure 1 in assembled relation within the loop of a, high frequency induction heating apparatus;

Figure 3 is a side elevation of the apparatus of Figure 2 with the parts of the tooth in position for welding;

Figure 4 is a front elevation of the same assembly as shown in Figures 2 and 3;

Figure 5 is a side view of the completed abrasive tooth;

Figure 6 is an end view of the tooth of Figure 5;

Figure '7 is a fragmentary view of a small portion of the periphery of a. stone cutting disk showing a socket wherein may be inserted a tooth;

Figure 8 is a sectional view taken on the line 8-8 of Figure 7; and

Figure 9 is a side elevation of the disk with inserted abrasive teeth.

Referring first to Figure 1, a diamond abrasive piece [0 may be molded to the shape shown. I provide a diamond abrasive consisting of diamonds bonded with a non-ferrous metal bond. Preferably I proceed in accordance with Reissue Patent No. 21,165 to Edward Van der Pyl which describes the manufacture of diamond abrasives by mixing a quantity of crushed diamond bort with metal powder, pressing the mixture in a mold to make the desired shape, then sintering at a temperature high enough to form a strong, tough abrasive piece.

One widely used formula for diamond abrasive bodies in accordance with the Van der Pyl patent consists of 18.6% tin and 81.4% copper, by weight, in separate powders, which produces a tough but friable bond for the diamonds. The concentration of diamonds may vary, depending upon particular material to be ground, but as an illustrative example I may use 25% by volume of diamonds, the remainder metal powders, to form the bond.

I now provide a steel adapter H which in this case is U-shaped in cross-section or end view and has countersunk holes I2 through the legs of the U, there being a total of eight of such holes. I further provide some solder or brazing material which in this illustrative example is silver solder represented by the strip l3, Figure 1. The strip I3 is cut out of sheet solder to make a nice fit in the shallow groove M of the piece Ill.

I then assemble the parts, as well illustrated in Figures 2, 3 and 4, with the solder stri l3 in the groove [4 and between the piece In and the adapter II.

The assembly of the abrasive piece In and the adapter I l with the strip of solder between them is placed, as shown in Figures 2, 3 and 4, in a coil or loop (in this case a loop) 20 of an induction heating apparatus. It is desirable that the plane of the lower edge of the loop should come just about at the top of the piece In and this places the strip of solder l3 just beyond the plane of the edge of the loop and not within the volume enclosed by any loop. To that end I may mount the assembly of the piece I0 and adapter I l upon a block 2! resting on the table 22 of the induction heating machine. Furthermore, in order to have a slight pressure and a firm contact between the parts being welded or soldered together, I preferably place a weight as represented by a block 23 upon the top of the adapter II. The blocks 2! and 23 are made of non-conducting or di-electric material as otherwise they would absorb power from the loop 20.

With regard to the solder [3, any hard solder or brazing material can be used and this includes various brasses and various formulae for silver solder. Merely as an example, I find that a silver solder which consists of 55.82% Ag, 22.10% Cu, 17.19% Zn and 4.90% Sn, all parts by weight, gives very satisfactory results.

The loop '20 is hollow and cold water is pumped through it while the machine is in operation.

Any suitable size or shape of loop or coil can be connected into the machine, the loop being held in place by nuts engaging threaded nipples inside the nuts which at once deliver electric energy and also cooling water. Induction heating and welding machines required for this operation are available on the market; I have obtained very satisfactory results with a machine providing 1070 British thermal units per minute or approximately 20 kilowatts at a frequency of 375,000 cycles per second.

When the parts are assembled as shown in'Figures 2, 3 and 4 and the loop 29 is energized, the end of the adapter ll adjacent the piece l2 will heat up in a matter of seconds. Actually it will be red hot in about twenty seconds. It is kept at this temperature for merely a few seconds and then the power is turned off. Care should be exercised that no metal part shall touch the loop 20 as if it does a hole will be burned in the loop 20.

Although the end of the adapter I 1 adjacent the diamond abrasive piece :0 gets red hot, the diamond abrasive piece I0 which is definitely in the high frequency electromagnetic field does not get red hot and, in fact, remains comparatively cool. This is the important feature which enables me-to make satisfactory pieces by this welding or soldering or brazing process since were the 'piece ID to get red hot during the welding operation it would be ruined as an abrasive. The outer layer'of diamonds in the piece l0 would burn if it were red hot.

There are two phenomena involved in induction heating. One is hysteresis and the other is eddy currents. Around every conductor carrying electricity is a magnetic field. Ifthe current is alternating, the magnetic field reverses with the alternation. A reversing magnetic field generates an electromotive force in any conductor located in said field. Such electromotive force willcreate eddy currentsin a solidblock of conducting material. On the other hand, if the material is paramagnetic, in addition to the eddy currents" due to-the conductivity of the material there is the phenomenon of hysteresis, which-constitutes the movement of the molecules of the-material as they try to adjust themselves parallel to thema'gnetic linesof force which in this case change their direction 375,000 times a second.

Furthermore, the heating effect due to the eddy currents is less with high conductivity material such as copper than it is with relatively poor conductors such as iron. For these reasons it is found that the lower end of the adapter II can beheated red hot while the diamond abrasive piece I0 is still relatively cold.

web 34 connecting a pair of recesses 33 are drilled four holes 35 spaced the same as the countersunk holes I2. Enough abrasive teeth 31 are provided so that the adapters thereof will fill all of the recesses 33. Then the teeth are placed in position as shown and riveted to the disk by rivets passing through the holes and headed over in the countersinks of the holes l2. In'this manner a very strong and rigid abrasive wheel is produced which is useful as a stone cutting saw to out large blocks of granite or other hard rock.

Diamond abrasives are used only to grind hard materials because it would be extravagant to use them where aluminous abrasives or carbide abrasives would sufiice. For certain materials which may be hard but not too tough, diamond abrasive bonded with 'resinoid is preferred. But in the case of certain hard and tough materials, such Figuresfi to 9 illustrate the manufacture of a a stone cutting disk 38 having abrasive teeth 3!,

each tooth consisting of a-diamond abrasive piece I ii and an adapter I i. The disk 304s made of steel and in an actual case was 90' inches-in diameter.

recesses-33 being opposite each other, all asclearly shown in the drawings. Through theconnecting as granite, diamond abrasive bonded with metal bond is found to give the best results. Diamond abrasive bonded with metal bond is hard, tough and strong. It will grind granite readily, but a great deal of power is consumed in the operation. In the-use of this enormous saw30, whichis'i feet in diameter, the abrasive pieces ID are forced into the granite withgreat pressure. This pressure is trying to rip the pieces Ill from the adapters l l. A surer test of thestrength of the metallurgical union could hardly be devised. It has been found that the abrasive teeth made in accordance with this invention survive this test and the granite saw 30 is effective to cut granite.

The process of theinvention may be used for securing diamondabrasive pieces bonded with non-ferrous metal bond to ironor steel adapters or directly to iron or steel circular saws or iron or steel band saws or, in fact, wherever it is desired to attach such non-ferrous metal bonded diamondabrasive pieces toanythin'g made of iron orsteel.

It will thus be seen that there has been provided by this invention amethodin which the various objects hereinab'ove set .forth' together with many thoroughly practical tadvantagesare successfully achieved. Asvarious possible embodimentsrnightbe madeiof the mechanical features of-theabove inventionand asithe art herein .describedmightbe varied in various :parts, all without departing from the scopeof the invention, it. isito be .understoodtthat all matter hereinbefore set forth or shown in the accompanying drawings is to be interpretedasillustrative and not in' a limiting sense.

I claim:

The method of attaching a diamond abrasive piece consisting .of diamonds .bonded with .a metal bondthe major part of which is copper to a piece offerrousmetaLincluding the stepof forming on the diamond abrasive pieces a surface andforming on the piece of ferrous metal a surface which surfaces fit each other nicely; the stepof placing a flat stripof solder between. said surfaces said strip of solder contacting each surface sothat said surfaces arefacing each other with the strip of solder in between them; the step of pressingsaid surfaces towards each otherythe stepof placing the pieces with relation'to a loop of a high frequency inductionheating machine so that the strip of solder is justbeyond the plane of the edge of the loop. and not withinthe volume enclosed by any loop but with ,part of'the piece of ferrousmetal adjacent said strip of solder within the said volume enclosedbytheiloopythe 'step' of energizing the loop of the machine until the piece of ferrous'metal insaidvolume is fedhot REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 21,165 Van Der Pyl July 25, 1939 1,996,598 Taylor Apr. 2, 1935 2,200,281 Koebel May 14, 1940 2,216,908 De Bats Oct. 8, 1940 2,233,176 Melton et a1 Feb. 25, 1941 2,299,207 Bevillard Oct. 20, 1942 2,316,506 Doelker et a1. Apr. 13, 1943 2,358,459 Kelleher Sept. 19, 1944 6 FOREIGN PATENTS Number Country Date 286,823 Great Britain Mar. 15, 1928 OTHER REFERENCES High Frequency Brazing in The Welding Encyclopedia, Eleventh edition, 1943, published by Welding Engineer Publishing C0,, Chicago, Illinois, pages 691 and 694.

Product Engineering, February 1943, pages 102-104.

Carbide Tools Tipped by Induction Brazing, by Paul Miller in American Machinist, October 14, 1943, pages 106, 107.

Curtis, High-Frequency Induction Heating, 1944, pages 114 and 115, McGraw-Hill Book Company, 1110., New York, New York. 

